Processes and systems are disclosed for monitoring the usage of projectile weapons, such as small arms, artillery and projectile weapons mounted on weapons platforms, such as tanks, self-propelled artillery, armored personnel carriers and aircraft.
Many have proposed devices to monitor the number of rounds fired by an automatic or semi-automatic firearm. Generally speaking, the proposed devices are either used to record the number of rounds fired for later study or meant to warn the user before the magazine of the firearm becomes empty. Some of these devices count the number of rounds in a magazine; others assume that a full magazine has been inserted and count the number of rounds fired using a shot detector. A few devices have been proposed that record the time and date when a weapon was fired, particularly for use in criminal investigations. Yet other devices are currently in use on paint-ball guns for scoring, timekeeping and billing purposes. The proposed devices suffer from various shortcomings, such as false counting or missed shots. Devices proposed for use in criminal investigations typically provide amounts and types of information that are inadequate for reconstructing a crime scene.
The maintenance of firearms is of particular concern to the military, to law enforcement, to competitive users and to a lesser extent, shooters in general. Wear from use gradually degrades the reliability and accuracy of a firearm and in extreme cases can lead to the failure of the firearm and or potential injury to the operator. Wear can also lead to jamming, particularly in automatic and semi-automatic firearms. Maintenance schedules that are generally based on time in service completely ignore the firing schedule of a firearm. For example, when used in training, thousands of rounds can be fired in a period of several months while in other periods a firearm may remain completely unused. A monitor that can be used to relate the firing history to barrel wear would allow maintenance to be based on usage, thereby benefiting all users of projectile weapons.
An electronic apparatus has been proposed for determining the wear of the gun tube of an artillery weapon. Wear in an artillery gun tube is governed not only by the number of rounds fired but also by the charge, which may be varied with each round. The apparatus would use a strain transducer to detect that a shot had been fired and apply a weighting function, proportional to the strain level, to determine the charge. The weighted number of shots fired would then be stored in memory so that barrel wear could be estimated. Rates of wear on artillery barrels are greater than those of small arms due to factors such as propellant make-up and projectile type.
This approach fails to take into account the effects of temperature on barrel wear. If a series of rounds are fired the gun tube is heated and wear, which results from the abrasive properties of the propellant, corrosion by the expanding gases and thermal gradients through the tube wall, is greatly accelerated. The proposed apparatus is also of limited applicability to small-arms where the shock and vibration of ordinary handling could produce many false counts.
It has proposed to attach a shot counter to a firearm for use in a weapon maintenance program. As an example, the program might require the replacement of the extractor after 15,000 rounds have been fired. Firing would be detected by a micro-switch on the trigger, an inductance or piezoelectric transducer in the buffer, or an inertial switch that responds to the recoil of the weapon. These switches would complete an electric circuit containing a battery that allows an electrochemical plating process to proceed while the transducers are used in a passive system, providing the electric potential that drives the plating. Usage is monitored by comparing the thickness of the plated layer at one end of a transparent tube to a color-coded scale on or adjacent to the tube. As in the previous citation there has been no thought given to avoiding false counts through handling.
To avoid false counts, it has been proposed to employ an inertial switch comprising a pivoting, eccentric mass, a mechanical counter and a spring that allows a threshold acceleration to be set. This purely mechanical system is relatively large and difficult to implement on small-arms. It is also likely to undergo a change in threshold as the contact surface between the spring and the shaft wear during use. Clearly an electronic device is preferable for use with small-arms where size and weight are important concerns. Electronic devices generally provide more reliability than mechanical devices in adverse environments and weather conditions.
It has been proposed to use two micro-switches to provide input to a micro-controller that counts the rounds remaining in a magazine. An LCD display would be used to indicate this count. Insertion of a new magazine would be sensed by the first switch and the count would be reset thereupon. Firing would be detected by a second switch on the gun's slide.
This device cannot determine whether a round is in the chamber when a new magazine is inserted. A device has been proposed to resolve this ambiguity by allowing the user to increment the count indicated by the counting device. It has also been proposed to use an additional switch within the chamber to automatically adjust the count. Neither device can differentiate between a round that has been fired and one that has been ejected without firing as required when a weapon is to be made safe and the round in the chamber must be removed by the operator.
Others have sought to eliminate micro-switches in order to reduce cost and complexity while improving accuracy, reliability and sensor life. It has been proposed to use an inertial switch in combination with an acoustic sensor to detect firing. Handling shocks cannot cause false counts because an acoustic signal must occur simultaneously before the count is incremented. Similarly, an acoustic signal from a weapon fired nearby cannot increment the count unless a simultaneous recoil impulse is detected.
It has also been proposed to use an inertial switch that is adjustable; this makes it possible to set the acceleration level that will trigger a count so that recoil can be differentiated from handling shock. An additional benefit of such a device is the ability to adjust it to work on weapons with different recoil characteristics. A stated use of this shot counter is to record the number of shots fired during a firearm's lifetime for use in its preventative maintenance schedule.
A further device has been proposed that would use a Hall-effect device for counting shots fired from small-arms. A micro-processor would record in non-volatile memory, the time and date of each shot fired along with the direction, from a Hall-effect compass, for crime lab analysis. In common with many of the previously described devices, this counter cannot distinguish between the firing of a live round, the chambering of the first new round after the last shot in a magazine has been fired, or the deliberate or accidental ejection from the host weapon of an unfired round.
The most technologically advanced devices for monitoring the firing of a projectile have been developed for use in paintball guns. When used in commercial applications it is important to record the number of rounds fired and the amount of time that a gun has been used. It is also desirable to provide information such as firing rate, maximum firing rate and battery condition to the user and to communicate these data, along with the gun's identification number, back to a control center. These devices would use a temperature sensor to monitor the pneumatic canister that powers the projectiles. One proposes the use of a detachable device that fits onto the muzzle end of the barrel and additionally measures projectile velocity.
The main shortcomings of the aforementioned devices are their inability to be easily adapted for use on different weapons. Typically, they are difficult to retrofit to a variety of firearms. Furthermore, those devices that utilize inertial switches, thereby avoiding the potential miscounts that are inherent in other sensing systems, cannot easily be altered to accommodate the fitment of various accessories such as night-vision sights or sound suppressors that are common additions to firearms and that can substantially change the mass of the host weapon to which the device is fitted.